Use of ultrasonic vibrations to disperse a liquid in another liquid



United States Patent 3,361,680 USE OF ULTRASONIC VIBRATIONS T0 DISPERSEA LIQUID IN ANOTHER LIQUID Byron B. Bohrer, Rosemont, Pa., assignor toSun Oil Company, Philadelphia, Pa., a corporation of New Jersey NoDrawing. Filed May 13, 1963, Ser. No. 280,079 16 Claims. (Cl. 252-314)This invention relates to processes for dispersing one liquid in anotherby the use of ultrasonic vibrations. The invention provides a method forutilizing such ultrasonic vibrations more efiiciently than has beenpossible heretofore.

It is well known to disperse one liquid in another by the use of eitherultrasonic vibrations or motor driven agitators. An advantage of usingultrasonic vibrations is that this technique generally results insmaller size dispersed phase particles, i.e., a more stable dispersion.For example, a dispersion of hexadecane in water free of emulsifyingagents and stable for, say days can be prepared by means of ultrasonicvibrations. If a motor driven agitator were used, however, anemulsifying agent would generally have to be employed to obtain the samestability. Another advantage of using ultrasonic vibrations is that thedispersion is usually effected in a shorter time than when a motordriven agitator is used. A disadvantage of the use of ultrasonicvibrations to effect dispersion is that the power consumption isgenerally higher than that which results when a motor driven agitator isemployed.

The present invention provides a method for reducing the powerrequirements in a process for dispersing one liquid in another by theuse of ultrasonic vibrations. Such reduction is accomplished, accordingto the invention, by dissolving in the liquid to be dispersed a smallamount of an additional liquid, the vapor pressure of said additionalliquid being higher than the vapor pressure of the liquid to bedispersed and being within 360 mm. Hg of the pressure at which thedispersion is to be carried out.

Before describing the invention in detail several terms used in suchdescription will be defined. As used herein the term dispersion appliesnot only to stable dispersions of one liquid in another, i.e., toemulsions, but also to unstable dispersions of one liquid in another. Inan unstable dispersion the dispersed liquid will settle out and resultmtwo distinct liquid layers within a few minutes after the agitation orother dispersing mechanism is shut off, While in a stable dispersion,i.e., in an emulsion, such separation generally will not occur for daysor weeks. In

some applications, such as solvent extraction, it is important tointimately disperse one liquid in another and then rapidly separate theliquids. In other words, it is important to form an unstable dispersion.

The liquid to be dispersed, i.e., the dispersed or discon- :tinuousphase of the resulting dispersion, is referred to herein as liquid A.The liquid in which liquid A is to be dispersed, i.e., the continuousphase of the resulting dispersion, is referred to herein as liquid B.For example, in a dispersion of oil in water, A is oil and B is water.

The temperature and pressure at which the dispersion takes place arereferred to herein as the system temperature and system pressurerespectively. Thus if oil is dispersed in water in a tank which is opento the atmosphere and maintained at 30 C., the system temperature is 30C. and the system pressure is atmospheric.

With reference to two given liquids, the term immiscible means thatmixtures of equal volumes of the two liquids will contain two distinctlayers. Similarly the term miscible means that a mixture of equalvolumes of the two liquids is a single homogeneous phase.

As described, the present invention provides a means for reducing powerrequirements in a process for ultrasonically dispersing liquid A inliquid B. Liquids A and B can be any two liquids so long as one of them(A) can be dispersed in the other (B). Liquids A and B will, of course,be immiscible at the dispersion conditions, i.e., at the systemtemperature, for this is inherent in the concept of dispersion.Preferably the solubility of liquid A in liquid B is less than 0.1% byweight at the system temperature. Typical dispersion processes to whichthe invention is applicable include processes for dispersing an organicliquid in water (e.g., oil in water), an organic liquid in an organicliquid (e.g., oil in methanol), an inorganic liquid in an organic liquid(e.g., water in oil), an organometallic compound in Water (e.g.,dirnethylsilicone in water), etc.

Since certain types of dispersions are in frequent use the invention ispreferably applicable to processes for creating such dispersions. Onesuch dispersion is a dispersion or an organic liquid in water. Forexample, oil in water dispersions are used as spray oils to protectfruit, etc. against insects. Similarly chemical reactions involvinghydrocarbons and effected by biological techniques often employ adispersion of the hydrocarbon in water. Thus fermentation of hexadecaneis effected by placing certain bacteria in a dispersion of hexadecane inwater. Another common dispersion is a dispersion of water in oil. Thistype finds frequent use in, for example, hydraulic fluids.

The relative amounts of liquids A and B is not critical and will varydepending upon the nature of the specific liquids employed, the ultimateuse to which the dispersion is to be put, etc. Normally the amount of Awill be 0.5 to 50.0% of the total Weight of A and B. All percentages inthis specification are by weight.

As previously described the power required to ultrasonically disperse Aand B is reduced by adding a small amount of an additional liquid,hereinafter referred to as liquid C, to liquid A prior to saiddispersing. Liquid C has certain characteristics as follows: it shouldbe mis cible with A at the system temperature. In addition, it should beimmiscible with B at the system temperature. Preferably the solubilityof liquid C in liquid B is less than 0.1%. Liquid C should also be inertto liquids A and B, i.e., it should not react with either during thedispersion process. In addition to the above characteristics, liquid Calso has certain vapor pressure characteristics. It should have a vaporpressure at the system temperature higher than the vapor pressure of theliquid to be dispersed, i.e., higher than liquid A. Furthermore, thevapor pressure of C at the system temperature should be within 360 mm.Hg of the system pressure. For example, when the dispersion is to becarried out at 1 atmosphere pressure (760 mm. Hg) the vapor pressure ofliquid C at the system temperature should be at least 400 mm. Hg. If thedispersion is to be efiectcd at 1 /2 atmospheres (1140 mm. Hg) the vaporpressure of liquid C should be at least 780 mm. Hg at the systemtemperature.

While liquid C should be a liquid at the temperature and pressure atwhich the dispersion of A in B is carried out, liquid C does notnecessarily have to be a liquid at room temperature and pressure. Forexample, in dispersing oil in water butane can be employed as liquid Cso long as the system pressure is sufficient to maintain the butane inthe liquid phase. Once the dispersion is effected the pressure can thenbe removed and the butane will, of course, vaporize and leave thesystem. Similarly a particular liquid may not have sufiicient vaporpressure at room temperature to be suitable as liquid C whereas if thetemperature at which the dispersion is effected is raised somewhat itmay be suitable as liquid C. For example, in a process for dispersingoil in Water at 22 C. and 760 mm. Hg, benzene is unsuitable as liquid Cbecause its vapor pressure at this temperature is only about 100 mm. Hg.However, if the same process is carried out at about 5560 C. benzenebecomes a suitable liquid C because at this higher temperature its vaporpressure is within the aforementioned vapor pressure requirements.

Since the vapor pressures and solubilities of various liquids arereadily available in the literature, the criteria for selecting liquid Care readily available to one skilled in the art. Where mineral oil isbeing dispersed in water, a preferred embodiment of the invention,compounds which can often be utilized as liquid C include butane,pentane, carbon tetrachloride, diisopropyl, butylethylene, etc.Preferably liquid C is a hydrocarbon. Where water is being dispersed inoil, compounds especially suitable as liquid C include low molecularweight (1-8 carbon atoms) alcohols, ethers, and ketones such asmethanol, acetone, and ether. Where hydrocarbons such as decane,hexadecane, etc. are being dispersed in water, compounds generallysuitable as liquid C include pentane, butane, diisopropyl, etc.Preferably liquid C is a hydrocarbon.

The amount of liquid C employed should be in the range of 0.01 to 2.0%by weight of liquid A. Within this range the amount will vary dependingupon such factors as the amount of liquid A being dispersed and thevapor pressure of liquid C. As the amount of liquid A increases, theamount of liquid C is preferably increased. Likewise, as the vaporpressure of liquid C decreases the amount of liquid C is preferablyincreased. In most cases the amount of liquid C will be, and preferablyis, 0.1 to 1.0% by weight of liquid A.

Since most dispersion processes are carried out at approximatelyatmospheric pressure, the invention is preferably applicable to such aprocess.

The magnitude of the reduction of power required to ultrasonicallydisperse A in B which is effected by adding C to A depends primarilyupon the differences in vapor pressure of liquids A and C. Where thisdifference is large the power reduction accomplished by the invention isrelatively large. As this difference decreases the power reductiondecreases. In view of this the invention is particularly applicable toprocesses for dispersing A in B wherein A has a low vapor pressure, Le,a vapor pressure less than 20% of the system pressure. An example ofsuch a liquid A is oil since most oils have vapor pressures of almostzero at room temperature. As already described, the invention ispreferably applicable to, inter alia, processes for dispersing oil inwater.

Although the invention has been described with reference to effectingdispersions solely by the use of ultrasonics, the invention is alsoapplicable to dispersion processes utilizing both mechanical agitationand ultrasonics. Thus it is desirable in some cases to form a very grossdispersion with a motor driven agitator after which this grossdispersion is subjected to ultrasonic vibrations to complete thedispersion. The reason for this is that it is sometimes more economicalfrom a power standpoint to form the initial dispersion mechanically eventhough ultrasonics must subsequently be used to achieve the desiredstability, dispersed particle size, etc. The present invention isapplicable to such a combination process. In such a case liquid C shouldusually be added to liquid A prior to the mechanical dispersion step.

The dispersion processes to which the invention is applicable, namely,processes for dispersing A in B ultrasonically, are well known in theart. Such processes are carried out in conventional equipment utilizingconventional means for generating ultrasonic vibrations. The most commonsuch means is the piezoelectric transducer although other means such asthe magnetostrictive transducer are also used. The frequency of theutrasonic waves generally employed in the dispersion of one liquid inanother is 10,000 to 20,000,000 cycles per second. Although theultrasonic range technically begins at about 20,000

c.p.s., frequencies of l0,00020,000 c.p.s. are often used in liquiddispersion processes, hence this range is included in the termultrasonic as used herein.

The dispersion processes to which the invention is applicable can alsoutilize an emulsifying agent in order to increase the emulsionstability. Conventional emulsifiers such as triethanolarnine stearatecan be used although the particular emulsifier employed will depend uponthe particular liquids A and B.

The advantage gained by the use of the invention in a process fordispersing one liquid in another is illustrated by the following.

Seventy-five parts water and twenty-five parts of a mineral oil having aviscosity of S.U.S. at 100 F. and an A.P.I gravity of 23 is charged at30 C to a mixing vessel open to the atmosphere and equipped with apiezoelectric tranducer. The oil-water mixture is subjected tountrasonic vibrations having a frequency of 30,000 c.p.s. for 3 minutes.The power input to the transducer is watts. After 3 minutes the oil isthoroughly dispersed in the water. The dispersion is stable for 36 hoursand is useful as a cutting oil.

Next the above procedure is repeated except that 0.125 part of n-pentaneis mixed with the oil before charging the oil to the mixing vessel.After subjecting the mixture to utrasonic vibrations (30,000 c.p.s. and150 watts input) for 2 minutes a dispersion stable for 36 hours isobtained. Thus the former requirements are reduced by 33%.

The invention claimed is:

1. In a process for dispersing a liquid, A, in another liquid, B,immiscible therewith by subjecting a liquid mixture of A and B toultrosonie vibrations, the temperature and pressure at which saidsubjecting takes place being the system temperature and system pressurerespectively, the improvement which comprises adding to liquid A, priorto said subjecting, 0.012.0%, by weight of A, of an inert liquid, C,which is miscible with A and immiscible with B, the vapor pressure of Cbeing higher than the vapor pressure of A and being within 360 mm. Hg ofthe system pressure, all said vapor pressures and all said miscible andimmiscible criteria being determined at said system temperature.

2. Method according to claim 1 wherein the solubility of both (1) A inB, and (2) C in B is less than 0.1%.

3. Method according to claim 1 wherein the vapor pressure of A is lessthan 20% of the system pressure.

4. Method according to claim 1 wherein the amount of C is 0.1-1.0% byweight of A.

5. In a process for dispersing an organic liquid in water atapproximately atmospheric pressure, said organic liquid being immisciblewith water, by subjecting a liquid mixture of said organic liquid andwater to ultrasonic vibrations, the temperature and pressure at whichsaid subjecting takes place being the system temperature and systempressure respectively, the improvement which comprises adding to saidorganic liquid, prior to said subjecting, 0.01-2.0%, by weight of saidorganic liquid, of an inert liquid C which is miscible with said organicliquid and immiscible with Water, the vapor pressure of C being higherthan the vapor pressure of said organic liquid and being within 360 mm.Hg of the system pressure, all said vapor pressures and all saidmiscible and immiscible criteria being determined at said systemtemperature.

6. Method according to claim 5 wherein said organic liquid is ahydrocarbon.

7. Method according to claim 5 wherein said organic liquid is oil.

8. Method according to claim 5 wherein liquid C is a hydrocarbon.

9. Method according to claim 5 wherein the solubility of both 1) saidorganic liquid in water, and (2) C in water is less than 0.1%

10. Method according to claim 5 wherein the vapor pressure of saidorganic liquid is less than 20% of the system pressure.

11. Method according to claim wherein the amount of C is 0. 11.0% byweight of said organic liquid.

12. In a process for dispersing water in oil at approximatelyatmospheric pressure by subjecting a liquid mixture of said oil and saidwater to ultrasonic vibrations, the temperature and pressure at whichsaid subjecting takes place being the system temperature and systempressure respectively, the improvement which comprises adding to saidwater, prior to said subjecting 0.01-2.0 by weight of said water, of aninert liquid C which is miscible with water and immiscible with saidoil, the vapor pressure of C being higher than the vapor pressure ofsaid water, and being within 360 mm. Hg of the system pressure, all saidvapor pressures and all said miscible and immiscible criteria beingdetermined at said system temperature.

13. Method according to claim 12 wherein liquid C is selected from thegroup consisting of low molecular Weight alcohols, ethers, and ketones.

References Cited UNITED STATES PATENTS 1,734,975 11/1929 Loomis et al252314 1,992,938 3/1935 Chambers et a1 252314 2,158,374 5/1939 Merrill252-312 2,304,125 12/1942 Shutt et a1 252-309 2,407,462 9/ 1946 Whiteley23 14 LEON D. ROSDOL, Primary Examiner. JULIUS GREENWALD, Examiner.

R. D. LOVERING, Assistant Examiner.

1. IN A PROCESS FOR DISPERSING A LIQUID, A, IN ANOTHER LIQUID, B,IMMISCIBLE THEREWITH BY SUBJECTING A LIQUID MIXTURE OF A AND B TOULTROSONIC VIBRATIONS, THE TEMPERATURE AND PRESSURE AT WHICH SAIDSUBJECTING TAKES PLACE BEING THE SYSTEM TEMPERATURE AND SYSTEM PRESSURERESPECTIVELY, THE IMPROVEMENT WHICH COMPRISES ADDING TO LIQUID A, PRIORTO SAID SUBJECTING, 0.01-2.0%, BY WEIGHT OF A, OF AN INERT LIQUID, C,WHICH IS MISCIBLE WITH A AND IMMISCIBLE WITH B, THE VAPOR PRESSURE OF CBEING HIGHER THAN THE VAPOR PRESSURE OF A AND BEING WITHIN 360 MM. HG OFTHE SYSTEM PRESSURE, ALL SAID VAPOR PRESSURES AND ALL SAID MISCIBLE ANDIMMISCIBLE CRITERIA BEING DETERMINED AT SAID SYSTEM TEMPERATURE.